In order to increase the operating safety of doors and/or gates that are to be opened automatically, the use of commercially available 3-D monitoring sensors is known. The latter signal a potential hazard situation when an object is detected in a hazard region situated as a result of the movement of the door to be opened and/or of the gate to be opened. By way of example, for this purpose they can communicate a corresponding signal to the relevant door and/or gate controller.